"Talk to Me" radiates more energy than almost anything else onscreen this summer and showcases Don Cheadle at his kinetic best, which is saying a lot. Yet watching it becomes an exercise in frustration when a potentially great movie winds up buried inside a just OK one. All the filmmakers had to do was keep the focus on Cheadle as real-life firebrand radio and TV personality Ralph Waldo "Petey" Greene instead of dispersing it on someone else nowhere near as riveting.

You can see what "Talk to Me" might have been in an electric opening scene of Petey shouting into a mike "Wake up, goddamn it" then slowly dragging on a cigarette. It's 1966, and although incarcerated he has persuaded the authorities to let him chatter on air and spin some discs for his fellow inmates.

It would seem that Petey's subsequently talking his way out of prison and onto a Washington, D.C., radio station, where in an era before political correctness he riles up audiences by speaking his mind, would be more than enough story, especially as it becomes evident that for all his bravado, the subject of this biopic is a tortured soul continually on the verge of self-destruction. Cheadle vividly captures his lows -- Petey is predisposed to turn up drunk at crucial moments -- as well as his highs, strutting around in a red velvet suit and paisley tie.

But then "Talk to Me" abruptly veers off into a parallel story of the station's program director Dewey Hughes (Chiwetel Ejiofor), the first to recognize Petey's ability to connect with D.C. audiences. Dewey is not without interest, a proud man who grew up in the projects, made it on his smarts and has no sympathy for his downtrodden brothers, including his actual one, a prison mate of Petey's. But as Dewey assumes more control, orchestrating his protege's career on television and landing him a coveted spot on Johnny Carson, "Talk to Me" becomes a movie divided against itself.

Although Ejiofor projects a presence and was memorable in "Inside Man," he's no match for Cheadle. When Dewey establishes his street cred by demolishing Petey at pool, it's Cheadle's angry reaction to the humiliation you'll be looking at, not Ejiofor's smug smile.

Dewey is in awe of Petey's talent and secretly jealous of it, Salieri to his Mozart. These are easily relatable emotions. But when Dewey reveals himself to be a surprise natural on the airwaves, "Talk to Me" loses credibility. Even if everything really happened exactly this way, it's a lesser movie for deflecting attention from the more compelling character. Only after a careful reading of the production notes does the reason for this catastrophic shift in direction become clear. One of the screenwriters, Michael Genet, is Dewey Hughes' son.

Despite a muddled script, director Kasi Lemmons ("Eve's Bayou") does a commendable job capturing the tumultuous period following the assassination of Martin Luther King Jr. In almost documentary style, she re-creates the chaos and looting on the streets. The filmmaker also shows an innate understanding of Petey, who for all his erratic behavior becomes a voice of reason and helps end the rioting.

Lemmons has assembled a fine supporting cast, including a relatively subdued Cedric the Entertainer (if you can imagine such a thing) as an old-style DJ who's still playing the Supremes while listeners are panting for James Brown, and Martin Sheen as the station owner who reluctantly agrees with Dewey about the need for a change. His presidential sheen brings dignity to a role that could have slipped into caricature.

As much as the screenplay allows, however, this is Cheadle's movie. Petey's signature sign-on was "talk to me"; but it was his patter that seduced audiences. Words tumbled out of his mouth. Considering the extreme verbiage, a surprising number of them were positively poetic like his favorite admonition: "I'll tell it to the hot; I'll tell it to the cold; I'll tell it to the young; I'll tell it to the old. I don't want no laughin', I don't want no cryin', and most of all, no signifyin'."

-- Advisory: Sexuality and language.

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